FORT WORTH (CBSDFW.COM) – The Amber Alert issued Tuesday for an 11-year-old Fort Worth girl is still in effect two days later, and has officially been extended as the FBI steps in to help. Jessica Smith is believed to have been taken by her mother.

Jessica is 5 feet 1 inch tall, weighs approximately 120 pounds, has brown eyes and straight brown hair. She regularly wears glasses, as seen in her photos, but is not believed to have had them when she was abducted.

The young girl is a fifth grader at Parkwood Hill Intermediate School in the Keller Independent School District. Police were contacted by Jessica’s school when she did not show up for classes on Tuesday morning.

Jessica and her mother were last seen at their home in the 7300 block of Indiana Avenue in Fort Worth. The mother is 42-year-old Kimberly Smith. She is 5 feet 2 inches tall and weighs about 150 pounds. Kimberly has a tattoo of a cross on the back of her neck, and another decorative tattoo on her back. Kimberly is believed to be driving a 2007 silver Mazda CX-9 with the Texas license plate BMZ-390. The car has tinted windows and a pink and green Harley-Davidson decal in the rear window.

There have been reported sightings of the mother and daughter in both Corpus Christi and New Mexico. When this case became a multi-state investigation, the FBI stepped in to assist.

An argument between Kimberly and some other family members got heated on Monday night at their Fort Worth home, just before the mother and daughter disappeared. CBS 11 News spoke with Jessica’s older sister, 16-year-old Caitlin Fields, who said that there have been some recent issues in the family. “It’s kind of just personal stuff that’s been going on for a while. Jessica’s been talking to her counselor about it and I guess my mom didn’t want her to,” she said.

Kimberly is in the middle of a divorce, and struggling.

When asked if she thought Jessica was in danger, Caitlin said, “I like to hope not. But there’s no telling because my mom’s never done anything like this.” However, police said on Wednesday that Kimberly has a history of mental illness and has threatened to commit suicide and hurt her children. Family members said that she threatened to do so as recently as Monday night.

Jessica’s father, Phillip Smith, also is facing charges of sexually assaulting a child. He was arrested in October. Court papers show that he is accused of inappropriately touching his daughter. Tom Pappas, Phillip Smith’s attorney, said that depositions were approaching in the next few weeks. “We are very, very comfortable that it’s a false outcry,” said Pappas. “What we’ve learned today — I can’t go into the details — verify, in fact, it was a false outcry.”

“He is worried sick over his daughter,” added Pappas, “and he will do whatever he needs to do to make sure she is safe.”

Tammy Vu is one of Jessica’s friends. She said that, on a normal day, the little girl would have been outside playing, her voice echoing throughout the neighborhood. “I really want to find her, because she’s my best friend,” Tammy said.

“I don’t know if we’ve underestimated her, or if we’re overestimating her,” Caitlin said. “I just hope we can all get through it, and Jessica is okay, and my mom gets some help.”

Anyone with information on Jessica Smith’s whereabouts, or the whereabouts of Kimberly Smith, is urged to call 911 or contact the Fort Worth Police Department at 817-335-4222. There is also a Facebook page dedicated to finding Jessica.